1. Field of the Invention
The present invention relates to a method and a device for producing a cutting or embossing roller by means of laser resurfacing welding, particularly for use in an envelope or label production machine, for cutting or embossing moving material webs or moving individual cutouts. The invention furthermore relates to a cutting or embossing roller produced using this method. The invention also relates to the use of a powder composition for producing a cutting or embossing roller of this type, by means of laser resurfacing welding.
2. The Prior Art
In envelope or label production machines, cutting or embossing rollers rotate at a relatively high speed of rotation, in order to perform cuts or embossed regions on moving webs of paper or moving individual cutouts. The paper to be cut or embossed contains metallic and non-metallic components as well as earths and clays. As a result, the cutting or embossing projections are exposed to significant stresses and subject to great wear. For this reason, it was usual, some time ago, to mill the knife blades of cutting rollers from solid material. Accordingly, the entire cutting roller consisted of a high-quality material that would actually have been required only for the cutting knife, i.e. the knife blade, according to the profile of requirements. The result was high costs in the production of the cutting rollers.
In DE 29 07 325 A1, it was therefore proposed to form the cutting knife by welding onto the base body of the roller welding beads made of a high-alloy, wear-resistant, and relatively hard steel. In this way, the base body of the roller could be produced from a lower-quality and therefore inexpensive material, as compared with the blade material. Application of the welding beads in the sense of this known method took place by means of electrical wire welding. This welding method requires a relatively large amount of time for applying the weld seams to the base body of the roller. This welding method also causes undesirable weld splashes on the surface of the base body of the roller, and not infrequently results in bubbles and/or cracks in the weld seams. These bubbles or cracks reduce the ability of the cutting knives, which are subject to great stress, to withstand mechanical stress, and thereby reduce their useful lifetimes.
Another welding method, namely laser resurfacing welding, is known from DE 198 32 185 A1, for example. There, the use of a diode laser, in particular, is proposed for carrying out the laser resurfacing welding. This laser melts an additional material in powder form, in order to thereby repair molding dies for injection molding and die-casting.
Another use of laser resurfacing welding, which process is actually known, is described in DE 195 33 960 A1, but not with a diode laser. There, metallic molding dies are produced, in that a powder that contains metal is melted in layers, in a melting region of the laser beam, and the applied layers are subsequently cut by machine. It was recognized that a not insignificant aspect in conducting the process of layer-by-layer construction of the work piece by means of melting the powder consists in the temperature of the work piece. Only if every layer is produced under the same conditions can the desired homogeneity with the related good mechanical properties be achieved. For this reason, a temperature measuring system is proposed. This temperature measuring system detects the surface temperature of the work piece after a layer is cut and causes the further layer-by-layer construction of the work piece to take place only if the detected temperature does not exceed a pre-determined value. This requirement, of course, results in time delays in the production sequence.